Solid-state imaging readers, that are configured either as vertical slot scanners each having a generally vertically arranged, upright window, or as flat-bed or horizontal slot scanners each having a generally horizontally arranged window, or as bi-optical, dual window scanners each having both generally horizontally and vertically arranged windows, or as stand-mounted, stationary scanners having a presentation window, have been installed as workstations in many venues, such as supermarkets, department stores, and other kinds of retailers, as well as warehouses, and other kinds of industrial settings, for many years, to electro-optically read by image capture a plurality of symbol targets, such as one-dimensional symbols, particularly Universal Product Code (UPC) bar code symbols, and two-dimensional symbols, as well as non-symbol targets, such as driver's licenses, receipts, signatures, etc., the targets being associated with objects or products to be processed by the workstations. An operator or a customer may slide or swipe a product associated with, or bearing, a target in a moving direction across and past a window of the workstation in a swipe mode. Alternatively, the operator or the customer may momentarily present the target associated with, or borne by, the product to an approximate central region of a window, and steadily momentarily hold the target in front of the window, in a presentation mode. The choice depends on user preference, or on the layout of the workstation, or on the type of the target.
Known imaging workstations typically include an imaging scan engine or module for supporting a solid-state, image sensor or imager comprising an array of pixels or photosensors, for sensing return light returning through a window of the workstation from a target being imaged. The image sensor may be a one- or two-dimensional charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) device, operable at a frame rate, and is analogous to the image sensors used in electronic digital cameras. The known imaging workstations also typically include an illuminating light system for illuminating the target with illumination light from an illumination light source, e.g., one or more light emitting diodes (LEDs), through the window of the workstation; an imaging lens assembly, e.g., one or more imaging lenses, for capturing return ambient and/or illumination light scattered and/or reflected from the target through the window of the workstation over a reading field of view and over a range of working distances relative to the window; and electrical circuitry for producing electronic analog signals corresponding to the intensity of the light captured by the image sensor over the reading field of view, and for digitizing the analog signal. The electrical circuitry typically includes a controller or programmed microprocessor for controlling operation of the electrical components supported by the workstations, and for processing the target and/or decoding the digitized signal based upon a specific symbology when the target is a symbol.
Some known workstations continuously capture and attempt to process and/or decode targets without regard to whether or not a target is actually in the reading field of view of the scan engine. However, continuous, repetitive, flashing of bright intense light from the LEDs of the illuminating light system consumes and wastes energy, degrades component lifetimes, and can be perceived as bothersome, distracting and annoying to the operators of the readers and to nearby consumers being served.
To alleviate these problems, the art has proposed periodically activating, i.e., waking-up, the imaging scan engine with a few different approaches. For example, the imaging scan engine can be operated with a very low duty cycle (about 10%). Thus, the imaging scan engine wakes up for a very short period of time to scan the reading field of view and tries to detect a presence of a target therein. However, this creates sluggishness in the reader's performance and delays in decoding, which can be perceived as an engineering defect. Also, the distracting flashing illumination light is still present during the wake-up time period.
Another approach for the imaging scan engine tries to detect the target without energizing the illumination LEDs. However, under low ambient light conditions, for example, when a reader is located in a dark corner in a retail environment, the activation time will be slow since the exposure of the image sensor has to be very long in order to acquire an image of acceptable brightness for object detection. Again, the reader's performance is sluggish.
Still another approach is to install an object sensing system inside the workstation, for activating the scan engine, e.g., the illuminating light system, only if an object or product bearing, or associated with, a target is detected within the active reading field of view of the scan engine. The object sensing system has one or more object light sources for emitting object sensing light, typically infrared (IR) light, and at least one object sensor for sensing the return IR light reflected and/or scattered from the object over an object detection field of view. Although generally satisfactory for its intended purpose, the use of an object sensing system is disadvantageous, because a portion of the IR light incident on the window of the workstation is reflected therefrom back into the object detection field of view of the object sensor. This reflected portion of the IR light creates undesirable hot spots in the object detection field of view and may significantly compromise object sensor performance.
Accordingly, there is a need for an apparatus for, and a method of, illuminating and reading all the targets presented to a workstation, without bothering, distracting and annoying the operators and/or consumers by exposing them to continuous, repetitive, flashing of bright intense light from the illuminating light system.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.